Aluminum alloys



-. the copending application.

Patented Sept. 5, 1944 ALUMINUM ALLOYS Walter Bonsack, South Euclid,Ohio, assignor to The National Smelting Company, Cleveland, Ohio, acorporation of-Ohio No Drawing. Application December 1, 1941,

Serial No. 421,244 f 4 Claims. (Cl. 75-141) This invention relates toalloys, and more part ticularly to machinable aluminum base alloys-having low thermal expansion and-relatively.

high wear resistance. Aluminum alloys having relatively low thermalexpansion, together with relatively high strength and hardness, andretaining these properties after exposure to prolonged hightemperatures, are especially desirablefor the manufacture of castings,such as pistons or other parts, for use in internal combustion enginesand the like.

Aluminum-silicon alloys containing suitable amounts of manganese andmagnesium have been used in the production of such pistons; and in thesealloys as the proportion of silicon is increased, the thermal expansionof the alloy is decreased, and thehardness and wear resistance of thealloy are increased. Their wear resistance, however, has not been asgreat as usually desired and'the expansion has not been lpw enough. Thisis because it has usually been necessary to have the percentage ofsilicon less than about 15%, as higher amounts of silicon have decreasedthe machinability and fatigue resistance of the alloy to a substantialdegree.

In my copending application Serial No. 388,491,

filed April 14, 1941, there is disclosed an'alloy containing silicon,magnesium, copper, iron, zinc,

tin, and at least one or more elements such as manganese, nickel,chromium, cobalt, titanium, columbium, molybdenum, tungsten, vanadium,zirconium, boron, tantalum and cerium. It has now been found that a verydesirable alloy may be obtained without utilizing tin as specified inThe tin may be replaced by the zinc or partly by the Zinc and otherhardeners, as will be more fully explained hereafter. a

The alloys of the present invention contain 18% to 35% silicon, about.l% to 1% magnesium, about .3% to 4% copper, about .4% or amount fromabout 20% to'.30% of the alloy. Silicon increases the hardness and wearresistance,of the alloy and decreases its thermal expansion. Withoutsuitable quantities of the other above mentioned constituents, however,it has a tendency to crystallize into relatively large crystals andtQ-decrease the machinability of the alloy.

Iron tends to harden the alloy, decrease its thermal expansion, increaseits machinability, and aids in maintaining the properties of the alloyat relatively high temperatures. It is preferably present within theamounts of about .7 to 1.5%, although an alloy having very desirableproperties may be obtained with 2% or so iron present, and with aslittle as about .4% or .5%. Iron, however, like silicon, has theproperty of tending to crystallize into relatively large crystals in theabsence of hardening metals of the/ groups set out above.

The members of the above groups each tend to harden the alloy, decreaseits thermal expansion and increase its machinability. They are alsobeneficial in that they tend to maintain the desirable properties atrelatively high temperatures, such as those encountered in internalcombustion engines and the like.

Metals of the above group of hardening metals consistingof manganese,nickel, cobalt and chromium are usually most desirable in the alloy forthe reason that they are more easily alloyed with the aluminum and mostdesirable properties are obtained whenat least one of these metals ispresent. These four elements function in aluminum alloys as hardenersand have no appreciable function as grain refiners.

.5% to 2% iron, about .3% to 4% zinc, and at least one' of the hardeningmetals selected from the group consisting of manganese, nickel,chromium, cobalt, titanium, columbiuml molybtantalum and cerium in atotal amount of 5% or less. Preferably, one or more of the elementsmanganese, nickel, chromiumv and cobalt are present in the alloy in asubstantial amount (.3% or more) with a total not substantially inexcess Ihe hardening and grainrefining metals of the group consisting ofcolumbium, molybdenum, tungsten, vanadium, zirconium, cerium, titanium,tantalum and boron are generally recognized as being both hardeners andgrain refiners in aluminum alloys. If grain refining is not particularlydesirable, as when the whole casting denum, tungsten, vanadium,zirconium, boron, A

of 3%. Also, one or more of the remaining metals is preferably presentbut not substantially in. excess of 2%. The alloy should preferably havethe hardening metals present in amount of .3%

or more. 1

Silicon, which aside from aluminum is the predominant alloyingingredient, may be present in the alloywithin the limits of 18% to 355%;but, siiioon is preferably present in an is chilledsubstantiallysimultaneously, it may not be necessary to use any 01 theseelements. However, it is preferable to have at least one present eventhough one-or more of the above group consisting of manganesepcobalt,chromium and nickel be also present. I

The desirable proportions of the elements in the above mentioned groupswhich are effective to obtain my improved results"ar e different; Thus,desirable properties may be obtained with any of the following elements:manganese in amount of about .2% to 1%; nickel in amount of about'.2% to1.5%; chromium in amount of about .l% to .5%; cobalt in amount of about.1% to .5%; columbiurn in amount of about .01% to 25%; molybdenum inamount of about .l% to 5%; tungsten in amount of about .l% to ,5%;

vanadium in amount of about .1% to .5%; zirconium in amount of about.01% to .25%; cerium in amount of about .01% to 25%.; titanium in amountof about .05% to .3%; tantalum in amount of about .1 to .3%; and boronin amount of about .005% to .1%. l

Since each of these hardening metals vmay tend to crystallizein somewhatdifferent shapes, finer crystals and more desirable properties may beobtained in alloys having more than one of these metals present, each inrelatively smaller amounts than in alloys having thesame total effectiveamount" of a lesser number of these metals.

The members of the above mentioned groups have the desirable property oftending to inhibit the growth of the large iron and silicon crystals,especially when two or more of the members are present. two or more ofthese elements present, even though there be present a relatively largeamount of iron. However, with a relatively large iron content, asomewhat smaller total quantity of these elements may be used to obtainsubstantial ly the same properties in the alloy as when a smaller amountof iron is present.

The total quantity of the hardening and grain refining metals in theabove groups should be less than 5% and they Should be present in anamount of about .8% or more, and preferably 1% or more of the alloy. Inthe preferred alloys having manganese, chromium, nickel, and zinc,

with one of the grain refining and hardenig' group, such as titanium,present, the preferred amount of manganese is about .'7%; the preferredamount of nickel is around l%; the preferred amount of chromium isaround .2%; and the preferred amount of titanium is about .15% to 2%.

Magnesium, as well as improving the hardness and tensile strength ofaluminum-silicon,

alloys, increases the elastic properties of the alloy, and also improvesthe machinability, and is preferably present in amounts of about .3%to-about .8%, although as much as 1%, or even somewhat more, may beused, and an appreciable effect is obtained with as little as about .1%.

Copper is animportant ingredient of my improved alloy and is preferablypresent in amounts of about 1% to 2%. strength, fatigue strength andhardness of the alloy, as well as improves its machinability. The

' amountof copper preferred depends to some extent on the zinc contentand the particular application to which the alloy is to be put. When thezinc is low it is often desirable to have more copper present. In casethe alloy is to be used as a bearing, it is desirable that both copperand zinc be present in the larger amounts. Zinc has the effect ofimproving the tensile strength and hardness of aluminlm alloys and alsoimproves the machinability and increases hardness. It

Consequently, it is desirable to have.

Copper increases the tensile The following examples illustrate thepresent invention:

Example 1 An aluminum base alloy containing 21% of silicon, about 2%copper; about .6% of manganese, about .4% magnesium, about .8% iron,about .4% nickel, about .5% of zinc, was chill cast into test bars,which were quenched from the mold and heat treated twelve hours at 355F. The hardness of the bars thus obtained averaged about 142 Brinell.Their tensile strength was about 30,500 lbs. per square inch.

The castings made from the alloy may be readily machined, haverelatively great wear resistance, relatively low thermal expansion andexcellent fatigue strength.

Example 2 When the zinc content of the alloy of Example.

' and heat treated twelve hours at 355 F., was becan be usedadvantageously in the present alloy I in amounts from about .3% to 4%,and it is preferable to have the zinc present'in amounts from about .'7%to about 2.5%.

Zinc even in the higher ranges has the property of remaining in solidsolution and does not separate from a cast;

sirable for parts which are subjected to hightemperatures.

tween 28,800. lbs. per square inch and 31,700 lbs. per square inch. TheBrinell hardness was between and 140. Castings made from the alloy werereadily machined and had very desirable wear resisting properties.

The alloys of the present invention are particularly desirable for theproduction of castings, and the castings are susceptible to the usualheat treatments and have their tensile strength and hardnesssubstantially improved thereby.

Furthermore, it is to be understood that various modifications of thealloys disclosed herein can be made without departing from my inventionas defined in the appended claims.

What I claim is:

1. An aluminum base alloy having a relatively low coefficient of thermalexpansion and relativelygreat wear resistance, containing 18% to 35%silicon, about .1% to 1% magnesium,-about .3% to 4% copper, about .4% to2% iron, about .3% to 4% zinc, and one or more of the hardening andgrain refining metals, with the balance substantiallyall' aluminum andminor impurities.

2. An aluminum base alloy'having a relatively.

low coefficient of thermal expansion and relatively great wearresistance, containing 20% to 530% silicon, about .1% to 1% magnesium,about ing and grain refining metals, with the balance' substantially allaluminum and minor impurities.

3. An aluminum base alloy having a relatively low coeflicient of thermalexpansion and rela-. tively great wear resistance, containing 18% to 35%silicon, about .3% to .8% magnesium, about 1% to 2% copper, about .'7%to 1.5% iron, about .'7% to 2.5% zinc, and one or more of the hardeningand grain refining metals, with the balance substantially all aluminumand minor impurities.

4. An aluminum base alloy having a relatively low coefficient of thermalexpansion and relatively great wear resistance, containing 18% to 35%silicon, about .1% to 1% magnesium, about .3% to 4% copper, about .4%to'2% iron, about -.3% to 4% zinc, and about .2% to 1% manganese, withthe balance substantially all aluminum and minor impurities. Y

. WALTER BONSACK.

